The United States Postal Service (USPS) publishes and maintains physical standards for articles to be sent through the mail. These standards describe the criteria used by the USPS to determine if letters, cards, and unenveloped mailpieces fit within the qualifications of “machinable”, “nonmachinable”, or “automation” classes of mail. Unenveloped mailpieces (such as, but not limited to, booklets, folded self mailers, or double postcards) are also subject to additional requirements related to the preferred method for sealing, or tabbing. Tabbing involves folding an adhesive backed film over any unbound edges to keep them secure. Failure to conform to these requirements can incur additional cost to the sender, delay delivery, or damage and jam high-speed mail processing equipment. In direct mailing and advertising applications, tabbing to ensure compliance with USPS machinable and automation requirements is crucial to reducing costs, and eliminates the need for an envelope.
One type of tab used with unenveloped mailpieces includes paper tabs. While paper tabs are easy to open, they are opaque. As a result, even the most translucent paper seals are disruptive to the appearance, content, and style of unenveloped mailpieces.
Another type of tab used with unenveloped mailpieces includes solid and perforated transparent polymer tabs. While solid and perforated transparent polymer tabs do not visually interfere with graphics and print material underneath, they suffer from several disadvantages. For example, the toughness of the solid polymer tabs prevent the seals from being easily torn or broken by the user, especially for the elderly. Because of the difficulty in breaking the solid polymer tabs, many recipients open the unenveloped mailpieces by tearing the paper around the solid polymer tab, thereby damaging the document and creating an unpleasant visual appearance.
While perforated polymer tabs allow recipients to open their mail by breaking the seal along the perforation, perforated polymer tabs proved to be problematic for the USPS, as they were prone to opening during the mailing process, jamming handling and sorting equipment. For this reason, the USPS now requires all tabbing to be done with nonperforated seals. See, USPS Quick Service Guide 20 lb. See, Mailing Standards of the United States Postal Service Domestic Mail Manual section 201.3.
Accordingly, there is a need for a tab that offers transparency, adequate adhesion, and ease of opening, while maintaining the required standards of the USPS, and not significantly increasing the cost of sealing unenveloped mail. Such a seal would also need to be compatible with current automatic tabber equipment.